EP4201648A1 - Thermal process control - Google Patents

Abstract

The invention relates to a method for thermal process control, with the aid of which three-dimensional objects (410) are produced by means of additive manufacturing by discharging volume elements of a certain size of at least one fluid solidifiable material at a certain temperature using at least one discharge nozzle of at least one discharge unit (630) of a process controllable Device for generating the three-dimensional object (410) at discrete positions in a space (610) according to a predetermined model of the object (410) can be generated. The model is part of a computer-implemented machine code and includes a close-to-reality model capable of adjusting local temperatures in order to realize homogeneous properties of the object (410) with an optimal fusion of the volume elements, never exceeding predetermined, material-dependent upper temperature limits in order to avoid melting or softening and/or deliquescence of material that has already been deposited and to ensure the dimensional stability of the object (410).

Description

The invention relates to a method for thermal process control with the features of the preamble of claim 1. According to the method, at least one three-dimensional object is produced by means of additive manufacturing by discharging volume elements of a certain size per unit of time of at least one fluid solidifiable material with a certain temperature using at least one discharge nozzle of at least one discharge unit a device that can be controlled by the method for generating the three-dimensional object at discrete positions in a construction space according to a previously defined model of the three-dimensional object. The model is part of a computer-implemented machine code that defines the discrete positions of the volume elements to be extracted and boundary conditions for their extraction. The temperature of the volume element is calculated for each discrete position in three-dimensional space, taking into account the thermal energy that is introduced into the installation space or removed from it by at least one heat source and/or heat sink and is released through heat losses in the installation space. Furthermore, the invention relates to a device for carrying out the method for extracting volume elements at discrete positions in a construction space, according to a model of the three-dimensional object and according to claims 15 and a computer program product according to claim 16.

From the DE 10 2016 120 998 A1 is a method for the simulation-based detection of thermally critical component areas in the additive manufacturing of a three-dimensional component from several component layers by multiple incremental, in particular layered, addition of powder, wire or strip-shaped, in particular metallic, component starting material and, in particular incremental, shaping hardening by respective selective Melting and/or sintering of the starting material for the component is known by means of an amount of heat introduced locally by at least one energy source. The method includes a simulation-based calculation of the values of the local heat dissipation capability in component layers of the manufactured component and identification of thermally critical component areas using the simulation-based calculated values of the local heat dissipation capabilities or using a function thereof. Furthermore, corresponding methods for component-specific local adaptation, in particular control or regulation, of local heat generation in the additive manufacturing of a three-dimensional component are known from this.

The DE 10 2017 107 362 A1 describes a method for the additive manufacturing of a three-dimensional component from several component layers by multiple incremental, in particular layered, addition of powder, wire or strip-shaped, in particular metallic, component starting material and, in particular incremental, shaping consolidation by selective melting and/or sintering of the component starting material by means of an amount of heat introduced by at least one energy source, in particular locally, according to a scanning strategy. The trajectories of the heat input are designed on the basis of a local heat dissipation capability that is determined, in particular based on simulations. Also described therein is a method for calculating a scanning strategy for the purpose of corresponding control of a system for additive manufacturing of a three-dimensional component and a related system.

From the DE 10 2017 107 364 A1 is a process for the additive manufacturing of a three-dimensional component from several component layers by multiple incremental, in particular layered, addition of powder, wire or strip-shaped, in particular metallic, component starting material and, in particular incremental, shaping consolidation of the component starting material by selective melting and/or sintering in each case known by means of an amount of heat introduced by at least one energy source, in particular locally, according to a scanning strategy. The method includes dividing each component layer into segments, with the division of a component layer into segments and/or the chronological order of the generation of individual segments and/or the layout of the scan vectors within a segment and/or the chronological order of the scan vectors within a segment upon generation of respective segmented component layers on the basis of a local heat dissipation capability determined, in particular based on simulation, or based on a function thereof in a respective component layer. Furthermore, a method for calculating the scanning strategy for the purpose of corresponding control of a system for the additive manufacturing of a three-dimensional component and a corresponding system are known from this.

In the DE 10 2018 127 678 A1 describes an additive manufacturing method that includes monitoring the temperature of a portion of a build plane during an additive manufacturing operation using a temperature sensor as a heat source traverses the portion of the build plane, detecting a peak temperature associated with one or more passes of the heat source through the portion of the assembly level, determining a limit temperature by reducing the peak temperature by a predetermined amount, determining a time interval in which the monitored temperature exceeds the limit temperature, identifying a change in manufacturing conditions that are likely to result in a manufacturing defect using of the time interval and changing a process parameter of the heat source in response to the change in manufacturing conditions.

The four documents mentioned above all deal primarily with the calculation of a simulation-based determined local heat dissipation capability when creating a three-dimensional object using additive manufacturing processes, although only parts of a heat energy model that comes close to reality are considered and for controlling an optimized manufacturing process, especially with regard to optimal local heat dissipation Temperatures when discharging the solidifiable materials are used.

From the US 10,442,118 B2 a 3D printing system is known in which the part quality of 3D printed parts should be better controlled. For this purpose, the temperature of an extruder filament is determined using a secondary heat source, with a z. B. Infrared heat source can be used to heat the 3D printer filament to the optimum temperature that enhances the welding of the filament to a substrate being printed on. Such an optimal temperature may be based in part on the temperature of the substrate. An intelligent controller can be used to receive temperature readings of the substrate and/or filament to then adjust the temperature of the heating source.

In the U.S. 10,710,353 B2 describes a process for additive manufacturing using fused deposition modeling (FDM) that is improved by laser preheating of the target substrate in front of the extrusion nozzle. Higher interface temperatures result in improved wetting, diffusion, and randomization, which improves interfilament and interlayer bonding and reduces anisotropy in the resulting finished part.

The WO 2017/210490 A1 describes a method for printing at least a portion of a three-dimensional object, comprising receiving a model of the 3D object in a computer memory and dispensing at least one filament material onto a substrate, thereby depositing a first layer that forms a portion of the 3D object adjacent to the substrate corresponds. A second layer corresponding to at least another part of the 3D object can be subsequently deposited. At least a first energy beam from at least one energy source can be used to selectively melt at least a portion of the first layer and/or the second layer, thereby forming at least a portion of the 3D object.

From the WO 2015/167896 A1 discloses an apparatus, system and method for 3D printing in which an interlayer bond in objects produced thereby is enhanced by one or more targeted heat sources that selectively preheat a portion of the existing object material before additional material is added to the object. 3D printing is also enhanced, optimized or calibrated by pre- or post-heating a target area. Targeted heat sources can be fixed, mobile, or a combination of these to apply heat to targeted areas. Such a heat source can be integrated into an existing 3D printer or integrated as an add-on to it. A controller of such a heat source can use 3D printer information, such as a current direction or a future print direction, to select one or more heat sources and perform other targeted heating operations, such as setting energy levels, aiming, moving, etc. The properties , e.g. B. The strength of 3D printed objects with improved interlayer bonding can be many times better than the same object printed without improved interlayer bonding.

The last four documents mentioned above all deal primarily with an improved generation of a three-dimensional object by means of additive manufacturing processes using additional heat sources, but essentially no simulation, in particular using a heat energy model that comes close to reality to control an optimized manufacturing process, in particular with regard to optimum local temperatures when discharging the solidifiable materials.

In the article " A HIGH FIDELITY THERMAL MODEL FOR A NOVEL DROPLET-BASED ADDITIVE MANUFACTURING PROCESS FOR POLYMERS" by Schroeffer, A., Maciuga T., Struebig, K. and Lueth, T., Proceedings of the ASME 2019, 14th International Manufacturing Science and Engineering Conference MSEC2019, June 10-14, 2019, Erie, PA, USA the basics of a largely precise thermal model for a droplet-based additive manufacturing process using polymer material are presented. The model used therein, which is part of a machine code for controlling a device for the production of three-dimensional objects, takes into account the heat energies that are introduced into the construction space by at least one heat source and given off by heat losses in the construction space to calculate the local temperature of a discharged drop of material Plastic, in particular thermoplastic material. In addition to the thermal energy introduced by discharge nozzles and additional heat sources, the thermal energy released into the installation space, e.g. B. the heat transport to a carrier carrying the object to be produced or to neighboring plastic drops that have already been discharged, the thermal radiation into the installation space and the free convection in the installation space are taken into account. Theoretically, the temperature development in the construction space is considered using a finite element method, but no conclusions are drawn from this for the further construction progress. An iterative and heat-energetically additive component of the discharged droplets is not taken into account, which influences the thermal energy balance in the installation space with regard to the qualitative fusion of the individual droplets with one another.

The U.S. 2018/314235 A1 discloses a system and method for optimizing toolpaths based on thermal/structural simulations of a part produced with a three-dimensional (3D) printer, and a non-transitory computer-readable medium encoded with executable instructions for performing the method. The system and method uses a Direct Energy Deposition (DED) 3D printing process in which a laser is used to melt a surface of an already discharged liquefiable and solidifiable material, with further liquefiable and solidifiable material being injected into the melted material powder form is introduced by means of a nozzle which is coupled to the laser. The temperature of the liquefiable and solidifiable material can be adjusted by adjusting the laser power, the travel distance of the nozzle with the laser (duration without laser effect), the duration of the laser effect and the width of the laser beam.

The EP 3 960 332 A1 discloses an additive manufacturing method for generating a manufacturing condition for additive manufacturing of a metal structure, additive manufacturing support software that supports generation of a manufacturing condition for additive manufacturing of a metal structure running on a computer, and an additive manufacturing constraint support system , which supports a manufacturing condition for the additive manufacturing of a structure by a manufacturing device. The method and the system also works with a Direct Energy Deposition (DED) 3D printing process, in which a surface of an already discharged liquefiable and solidifiable material is melted using a laser, with the liquefiable and solidifiable material being poured into the molten material solidifiable material in powder form is introduced by means of a nozzle which is coupled to the laser. The temperature of the liquefiable and solidifiable material can be adjusted by adjusting the laser power, the traversing speed of the nozzle with the laser, the duration of the laser effect and a preheating temperature of the material that has already been discharged or a construction platform, which can be adjusted using additional heat sources.

The two last-mentioned documents have in common that in the printing processes used therein, powdery, liquefiable and solidifiable material is discharged by means of a nozzle and is melted by means of a laser at the point of discharge on a construction platform or on previously discharged liquefiable and solidifiable material. In the invention described here, in contrast to this, liquefiable and solidifiable material is melted in a discharge nozzle and discharged in liquid form.

The invention is therefore based on the object of providing a method for thermal process control, the use of the method in a device and a device for carrying out the method for the above-mentioned purpose and a computer program product in which a computer-implemented model of at least one three-dimensional object is used which is suitable for adjusting local temperatures in order to realize homogeneous properties of a generated three-dimensional object with an optimal merging of the volume elements.

This object is achieved with a method according to the features of claim 1, a device for executing the method according to the features of claim 15 and by a computer program product according to claim 16. Advantageously, previously specified, material-dependent upper temperature limits are not exceeded at any time in order to avoid melting or softening and/or deliquescence of material that has already been deposited and to ensure the dimensional stability of the three-dimensional object.

Advantageous developments are the subject matter of the dependent patent claims. The features listed individually in the patent claims can be combined with one another in a technologically meaningful manner and can be supplemented by explanatory facts from the description and by details from the figures, with further embodiment variants of the invention being shown.

According to the method, a thermal process is carried out in the additive manufacturing of at least one three-dimensional object by discharging volume elements of a certain size per unit of time of at least one fluid solidifiable material with a certain temperature at discrete positions in a construction space according to a predetermined model of the three-dimensional object. The model is part of a computer-implemented machine code that defines the discrete positions of the volume elements to be discharged and boundary conditions for their discharge, with the temperature of the volume element being calculated for each discrete position in three-dimensional space and the heat energies generated by at least one heat source and at least one heat sink are introduced into the construction space or removed from the construction space and are given off by heat losses in the construction space, must be taken into account. Since the temperature at the time of discharge and after discharge is included in the calculation, additive manufacturing can be influenced by adapting the machine code in such a way that material-dependent upper temperature limits are never exceeded. This makes it possible to avoid melting or softening and/or deliquescence of material that has already been deposited and to ensure the dimensional stability of the three-dimensional object.

In a first advantageous embodiment of the method, which increases the accuracy of the local temperature calculation, for each discrete position in three-dimensional space for calculating the temperature of the volume element, the heat energies that enter the installation space from the at least one discharge nozzle of the at least one discharge unit and/or at least one heat source and heat sink arranged in the installation space on the at least one discharge nozzle are introduced and discharged and which act on the volume element, and the heat energies that enter the installation space from the volume element to at least directly adjacent volume elements and as thermal radiation and free convection to the environment are given, are taken into account.

In a further advantageous embodiment of the method, which increases the accuracy of the local temperature calculation while at the same time reducing the computational effort, the thermal energies that are relevant for the calculation of the temperature of volume elements for each discrete position in three-dimensional space and that are generated by at least one heat source and at least a heat sink in and out of the installation space and are given off by heat losses in the installation space, enter into a differential equation within the model of the three-dimensional object and/or the machine code, wherein parts of the differential equation can be linearized to solve them.

In an additional advantageous embodiment of the method, which further optimizes the temperature distribution in the three-dimensional object, the temperature of the volume element can also be recalculated for at least one of the directly adjacent discrete positions and/or for at least one other discrete position and, based on this, the machine code and/or the boundary conditions for temperature increase and temperature decrease are adjusted for at least this discrete position.

If, in a preferred embodiment, the calculated temperature of any point on the surface that has already been discharged is above a defined temperature limit at a point in time, a specific number of calculation steps can advantageously be carried out before this point in time, in order to make adjustments to the machine code and/or the boundary conditions for the temperature increase and temperature decrease at least in the newly calculated time interval. This allows the temperature distribution in the three-dimensional object to be adjusted at any time.

In another advantageous embodiment of the method, which increases the accuracy of the local temperature calculation, a relative trajectory of the at least one discharge nozzle and possibly at least one additional heat source and heat sink arranged on the at least one discharge nozzle can be calculated from machine code commands with respect to the surface of a three-dimensional Article-carrying carrier, z. B. a construction table, and / or the object are determined.

The method is preferably carried out with foresight, ie at least before the material is discharged for at least one volume element or also for parts of the three-dimensional object or the complete three-dimensional object. This is done by predictively calculating the temperature of the volume element for each discrete position and influencing the at least one heat source and the at least one heat sink by adapting the machine code and the boundary conditions for temperature increase and temperature decrease. As a result, before the volume elements are created, their influence on the production of the object can advantageously be taken into account and influenced in order to optimize the object.

• das Verändern der Prozessgeschwindigkeit,
• das Steuern der abgestrahlten Leistung der mindestes einen Wärmequelle,
• das Steuern der mindestens einen Wärmesenke,
• das Einfügen von zusätzlichen Verfahrbefehlen oder auch Wartebefehlen,
• das Verändern der Reihenfolge der diskreten Positionen, an denen nacheinander Volumenelemente ausgetragen werden,
• das Verändern der Beschaffenheit von Fülllinien und/oder Konturlinien.

Another advantageous embodiment of the method, which provides alternatives for adjusting the local temperatures, can include adjusting the boundary conditions using at least one or a combination of the following measures:

• changing the process speed,
• controlling the radiated power of the at least one heat source,
• controlling the at least one heat sink,
• the insertion of additional movement commands or waiting commands,
• changing the order of the discrete positions at which volume elements are successively discharged,
• changing the nature of fill lines and/or contour lines.

In an advantageous embodiment of the method, depending on the absorption spectrum of the material used, one or more thermal radiation sources, such as e.g. B. infrared emitters and / or one or more non-thermal radiation sources such. As laser, LED and / or gas discharge lamps can be used.

In a next advantageous embodiment of the method, an additional forced convection can be caused to reduce the temperature of the volume element at the discrete position. B. at least one fan and / or at least one controllable heat sink can be used optionally.

In another advantageous embodiment of the method, at least two materials with different specifics can be used as fluid solidifiable materials for the purposeful adaptation of the properties of the three-dimensional object.

In an advantageous embodiment of the method, for the targeted adjustment of the properties of the three-dimensional object and to maintain its dimensional stability when using at least two materials with different specifics that do not tolerate the same necessary installation space temperature, with the installation space temperature set to the lower of the two temperatures, the temperature of the volume element that requires the higher fusion temperature can be increased or reduced for its application, and/or when the installation space temperature is set to the higher of the two temperatures, the temperature of the volume element that requires the lower fusion temperature can be reduced or increased for its application These steps can also be combined, i.e. a higher temperature with heating and/or a lower temperature with cooling can be applied to the possibly also neighboring volume elements. This also includes the possibility of subsequently increasing or reducing the temperatures at the discharge point after the volume element has been discharged.

Especially in multi-material systems, by specifically influencing the boundary conditions and the temperature/s, be it e.g. in the installation space, on the carrier or in the material itself, advantageous framework conditions can be created that also allow materials with different specifics to be reliably connected to one another or to unite.

In an advantageous embodiment of the method, when using more difficult to process materials, especially when using high-temperature materials such. B. PEI, PSU, PPSU, PEEK, PEAK, PEK or PPS, the necessary installation space temperature can not be realized, the temperature of the volume element can be increased to its order.

In another advantageous embodiment of the method, which also favors the diffusion of the volume elements and / or z. B. in the case of semi-crystalline plastics, the morphology development is influenced or specifically controlled, discharged volume elements can tempered after the filling line and/or contour line has been completely drawn out. In principle, the surface of a carrier carrying the three-dimensional object to be produced or of the three-dimensional object to be provided with volume elements can be heated/cooled not only during material discharge, but also without material discharge.

The development of morphology can be favored by deliberately maintaining or increasing or decreasing the ambient temperature. In particular, the temperatures in the installation space and those of the carrier, which can preferably be temperature-controlled, have an influence on the ambient temperature. Such a temperature-controlled builder can advantageously act as an extension of the installation space heating (same temperature settings), e.g. to ensure homogeneous temperature control of the three-dimensional object, e.g. by creating the same temperature conditions on all component sides. This helps to avoid tension and thus minimize distortion.

In a further embodiment of the method, by means of which the advantageous mechanical properties of the three-dimensional object can be predicted, a morphology development of the three-dimensional object can be determined on the basis of a temperature development by means of a simulation.

The object is also achieved by a device for carrying out the method. The task is also solved by a computer program product. For advantages in terms of a local adjustment of the temperatures in order to realize homogeneous properties of a produced object with an optimal fusion of the volume elements without exceeding material-dependent temperature limits, the computer program product is stored with a program code on a computer-readable medium for carrying out the method described above.

Further advantages result from the dependent claims and the following description of exemplary embodiments.

Fig. 1a, 1b

schematische Darstellungen eines ersten Volumenelements bzw. eines zweiten Volumenelements mit einer Molekülkette,

Fig. 1c

eine schematische Darstellung einer Verbindung der beiden Volumenelemente aus Fig. 1a und Fig. 1b mit miteinander verbundenen Molekülketten,

Fig. 1d

eine schematische Darstellung einer unvollständigen Verbindung der Volumenelemente aus Fig. 1a und Fig. 1b mit nicht verbundenen Molekülketten,

Fig. 2

eine schematische Darstellung eines der Erfindung zugrunde liegenden Wärmeenergiemodells,

Fig. 3

ein Flussdiagramm zur Verdeutlichung der Simulation,

Fig. 4a, 4b

schematische Darstellungen der Fülllinien bzw. Konturen eines dreidimensionalen Gegenstands,

Fig. 5

eine schematische Darstellung aneinandergereihter Volumenelemente, der Konturen und Füllung des dreidimensionalen Gegenstands aus Fig. 4a und Fig. 4b,

Fig. 6

eine erfindungsgemäße Vorrichtung zur Ausführung des Verfahrens,

Fig. 7

eine vergrößerte Ansicht von Austragseinheit und Bauraum.

The invention will now be explained in more detail on the basis of exemplary embodiments illustrated in the attached figures. Show it:

Figures 1a, 1b

schematic representations of a first volume element or a second volume element with a molecular chain,

1c

a schematic representation of a connection of the two volume elements Figures 1a and 1b with interconnected molecular chains,

Fig. 1d

a schematic representation of an incomplete connection of the volume elements Figures 1a and 1b with unconnected molecular chains,

2

a schematic representation of a thermal energy model on which the invention is based,

3

a flowchart to illustrate the simulation,

Figures 4a, 4b

schematic representations of the filling lines or contours of a three-dimensional object,

figure 5

a schematic representation of lined-up volume elements, the contours and filling of the three-dimensional object Figures 4a and 4b ,

6

a device according to the invention for carrying out the method,

7

an enlarged view of the discharge unit and installation space.

Description of preferred embodiments

Before the invention is described in detail, it should be pointed out that it is not limited to the respective components of the device and the respective method steps, since these components and methods can vary. The terms used herein are only intended to describe particular embodiments and are not used in a limiting manner. Furthermore, if the singular or indefinite articles are used in the description or in the claims, this also applies to the plural of these elements, unless the overall context clearly indicates otherwise.

The mechanical properties in extruding and melting 3D printing processes (FDM, AKF, etc.) are determined by the material properties themselves, as well as the bond strength of the deposited volume elements of variable size (filaments, drops, etc.). The bonding strength is in turn determined by the bonding process between neighboring volume elements that takes place during 3D printing, and this depends on the thermal boundary conditions.

The melting together of individual volume elements 110, 120 to form a material connection 150 depends on the interdiffusions and entanglements of polymer chains or molecular chains 130, 140 in the boundary layer of the binding partner. A prerequisite for the interdiffusion is a certain mobility of the molecular chains 130, 140, favored by a sufficiently high thermal level. The Figures 1a, 1b and 1c show this process for the connection of two volume elements 110, 120, which are drop-shaped here, to form a larger connected volume element 150, the connection 160 of the previously separated individual molecular chains 130, 140 in the form of an entanglement with one another being recognizable. However, not only drops but also strand-like filaments come into consideration as volume elements, since these are also volume elements discharged per unit of time.

In the case of amorphous polymers, this movement occurs above the glass transition temperature in the thermoplastic state. Accordingly, the thermal energy of the newly applied volume elements 110, 120 must be high enough to heat all of the binding partners in the interface above the glass transition temperature.

In the melting 3D printing processes, on the one hand, the contact temperature between the volume elements 120 or 150 that have already been produced and possibly already solidified on the three-dimensional object to be produced and/or the melt temperature of the volume element 110 to be newly deposited can influence the melting together of the volume elements 110 and 120 or 150 .

An increase in the temperature of the melt also causes a reduction in viscosity, although lower viscosities are sometimes not possible without causing thermal damage to the material. The ambient temperature is usually achieved by forced convection of heated air, the increase in this is limited by the dimensional stability of the material in question.

There is also a compromise to be made when setting the ambient temperature for multi-material printing, especially when the material melting points are far apart. If the respective melting point temperature is not reached, sufficient material fusion is not guaranteed and if the melting point temperature is exceeded, the respective material does not have sufficient dimensional stability, as a result of which the geometric properties of the three-dimensional object could be adversely affected.

Examples are the processing of the material combination ABS and TPU. A construction space temperature of 100°C is recommended for ABS and 80°C for TPU. While one temperature is too high for one material and dimensional stability can no longer be guaranteed during the process, the other temperature is too low for the other material, so that sufficient material fusion cannot take place. The processing of material combinations whose melting points are far apart is therefore hardly possible.

In addition, with high-temperature materials (such as PEI, PSU and PPSU as well as PEEK or PEAK, PEK and PPS), the necessary installation space temperature is over 200°C and is usually only technically feasible to a limited extent.

Furthermore, the temperature development of the volume elements 110, 120 during the 3D printing process depends on other thermal conditions, such as the material properties and the process parameters, such as pressure, discharge speed, flow rate through the discharge nozzle, etc., but also the geometrical conditions of the three-dimensional objects to be manufactured 410 ( 4 ) away. The size of the volume elements 110, 120 also influences the course of the temperature via the ratio of surface area to volume: smaller volume elements 110, 120 cool down more quickly (with the same shape).

If individual volume elements 110, 120 are placed close together in time, the temperature level is high and merging is promoted. In the case of large object cross sections, many of the volume elements 120, 150 that have already been deposited have (almost) already cooled down to the installation space temperature and are in the region of the thermoelastic state, ie they may have already solidified. If a new volume element 110 is placed directly next to it, volume elements 120, 150 that have been cooled to the installation space temperature will be heated or melted due to the higher temperature level, but the volume elements 110 and 120 or 150 can no longer seamlessly melt together because the average temperature level is not sufficient. Fig. 1d shows this, with the two molecular chains 130, 140 of the two original volume elements 110, 120 not being connected or entangled with one another.

The method presented below and the device for carrying out the method serve to solve the task described at the outset while achieving the above-described complete connection 150 of the individual volume elements 110 and 120 or 150 with a connection or entanglement 160 of the originally separate molecular chains 130, 140 .

For this it is necessary to use a model of the three-dimensional object that is as comprehensive as possible, with the aid of which the boundary conditions of the material discharge and the material connection of the original volume elements 110, 120 can be defined. The model can be based on an empirical, analytical or numerical approach.

The temperature profile of the surface of the object over time at the point where the material is discharged can be modeled using a differential equation, for example. The solution depends both on the movement commands for the respective three-dimensional object to be produced and on the environmental conditions during the construction process.

The temperature change dT in a volume element is linked to the change dQ _V of the heat via the heat capacity Cv: $$\mathrm{dT}=\frac{1}{{\mathrm{C}}_{\mathrm{V}}}{\mathrm{dQ}}_{\mathrm{V}}.$$

The variable relevant for the adhesion of a volume element is the temperature on the surface at the time of discharge. Therefore, the quantities C and Q are introduced as heat capacity or heat per area A. The quantities C and Q are always linked to a height Δz, which together with A defines a volume to which the heat change relates. Differentiating the above equation for time t gives: $$\frac{\mathrm{dT}}{\mathrm{German}}=\frac{1}{\mathrm{C}}\frac{\mathrm{dQ}}{\mathrm{German}}.$$

den Wärmefluss durch die Oberfläche des betrachteten Volumenelements 110. Dieser setzt sich im hier betrachteten Fall zusammen aus den Wärmeverlusten durch Wärmeleitung Q̇_W, Konvektion Q̇_K und Strahlung Q̇_S. Q̇_HS beschreibt die eingebrachte Wärme durch Wärmequellen, wie bspw. die Austragsdüse 210 und/oder von mindestens einer zusätzlichen Wärmequelle und/oder der Wärmemenge des abgelegten Materials. Somit ergibt sich für den momentanen Temperaturwert eines aktuell auszutragenden Volumenelements 110: $$\frac{\mathrm{dT}}{\mathrm{dt}}=\frac{1}{\mathrm{C}}\left({\dot{\mathrm{Q}}}_{\mathrm{W}}+{\dot{\mathrm{Q}}}_{\mathrm{K}}+{\dot{\mathrm{Q}}}_{\mathrm{S}}+{\dot{\mathrm{Q}}}_{\mathrm{HS}}\right).$$

Here describes $\frac{\mathrm{dQ}}{\mathrm{German}}=\dot{\mathrm{Q}}$

the heat flow through the surface of the considered volume element 110. In the case considered here, this is made up of the heat losses through thermal conduction Q̇ _W , convection Q̇ _K and radiation Q̇ _S . Q̇ _HS describes the heat introduced by heat sources, such as the discharge nozzle 210 and/or by at least one additional heat source and/or the heat quantity of the deposited material. This results in the instantaneous temperature value of a volume element 110 currently to be discharged: $$\frac{\mathrm{dT}}{\mathrm{German}}=\frac{1}{\mathrm{C}}\left({\dot{\mathrm{Q}}}_{\mathrm{W}}+{\dot{\mathrm{Q}}}_{\mathrm{K}}+{\dot{\mathrm{Q}}}_{\mathrm{S}}+{\dot{\mathrm{Q}}}_{\mathrm{HS}}\right).$$

$${\dot{\mathrm{Q}}}_{\mathrm{K}}=\mathrm{\alpha }\left({\mathrm{T}}_{\mathrm{Luft}}-\mathrm{T}\left(\mathrm{t}\right)\right),$$

$${\dot{\mathrm{Q}}}_{\mathrm{S}}=\mathrm{\beta }\left({\mathrm{T}}_{\mathrm{Umgebung}}^4-\mathrm{T}{\left(\mathrm{t}\right)}^4\right),$$

wobei T_Bauteil die Temperatur des herzustellenden dreidimensionalen Gegenstands in Abstand I_z von der Oberfläche verwendet wird.The following expressions can be used for the heat losses as an approach to reducing the calculation effort: $${\dot{\mathrm{Q}}}_{\mathrm{W}}=\frac{\mathrm{\lambda }}{{\mathrm{l}}_{\mathrm{e.g}}}\left({\mathrm{T}}_{\mathrm{component}}-\mathrm{T}\left(\mathrm{t}\right)\right),$$

$${\dot{\mathrm{Q}}}_{\mathrm{K}}=\mathrm{a}\left({\mathrm{T}}_{\mathrm{Air}}-\mathrm{T}\left(\mathrm{t}\right)\right),$$

$${\dot{\mathrm{Q}}}_{\mathrm{S}}=\mathrm{\beta }\left({\mathrm{T}}_{\mathrm{Vicinity}}^4-\mathrm{T}{\left(\mathrm{t}\right)}^4\right),$$

where T _component is the temperature of the three-dimensional object to be manufactured at a distance I _z from the surface.

2 clarifies this connection. The discharge nozzle 210 is shown therein, which is shown on its own and/or in connection with at least one additional heat source, which is movably arranged on the discharge nozzle 210 . Several discharge nozzles 210 of one or more discharge units 630 ( 6 ), e.g. B. for the simultaneous discharge of a material or several materials with identical or different specifics are present. The discharge can also take place sequentially. In principle, volume elements of a certain size are discharged per unit of time. From the at least one discharge nozzle 210 of the at least one discharge unit 630 and/or the at least one additional heat source, the heat energy Q̇ _HS 270 per time is transferred to the area A in the construction space 610 ( 6 ) brought in. By means of convection Q̇ _K 260 and radiation Q̇ _S 250 as well as thermal conduction Q̇ _W 280, heat energy is released from the discharged volume element 110 to the object 410 in the environment of the construction space 610 and the air, as a result of which their temperatures T _component 240, T _environment 230 and T Change _air 220. The quotient dT/dt 290 describes the instantaneous temperature change of the discharged volume element 110. The previously discharged volume elements 120 and their connections 150 are also shown.

Equation (1.4) is the formula for heat conduction in the stationary, one-dimensional case. The heat conduction depends on the thermal conductivity λ and the temperature difference over the length l _z and is only considered in the Z direction, i.e. not in the XY plane between the individual discharge points.

Equation (1.5) describes natural convection. Air circulation in the construction space 610 generated by blowers can be neglected. Equation (1.6) describes the heat transfer by radiation according to the Stefan-Boltzmann law. It is assumed that the surfaces of the surroundings have a homogeneous temperature T _ambient .

In order to further reduce the computational effort for solving ODE (1.3), the heat losses can be combined and linearized. Thus one would get: $$\frac{\mathrm{dT}}{\mathrm{German}}=\mathrm{\Gamma }-\mathrm{g}\ast \mathrm{T}\left(\mathrm{t}\right)+\frac{1}{\mathrm{C}}{\dot{\mathrm{Q}}}_{\mathrm{HS}}\left(\mathrm{t}\right)$$

Equation (1.7) together with the new parameters Γ > 0 and γ > 0 describes a surface with temperature losses that are linear in temperature. The new parameters can be material and location dependent. The solution for the linearized differential equation (1.7) is then: $$\mathrm{T}\left(\mathrm{t}\right)=\left[\mathrm{T}\left(0\right)+{\displaystyle {\int }_0^{\mathrm{t}}\mathrm{ds}\left(\mathrm{\Gamma }+\frac{1}{\mathrm{C}}{\dot{\mathrm{Q}}}_{\mathrm{HS}}\left(\mathrm{s}\right)\right){\mathrm{e}}^{\mathrm{\gamma s}}}\right]{\mathrm{e}}^{-\mathrm{\gamma t}},$$

With a known time profile of the radiated heat per time, Q̇ _HS (t) at location _ri , this equation gives the time profile of the temperature at this point.

If a local increase in temperature is necessary at the time of material discharge, this can be done by increasing Q̇ _HS .

During the entire construction process, the object surface temperatures can be calculated by modeling and modified by adjustments to the machine code that generates the three-dimensional object 410, which can also include the control of at least one heat source, at least one fan and/or at least one other controllable heat sink such that at the point in time when the material is discharged at the same location, these lie in a predetermined, material-dependent interval in order to realize homogeneous object properties with a sufficient merging of the volume elements 110, 120. Advantageously, a previously specified, material-dependent upper temperature limit is not exceeded at any time in order to avoid melting or softening and/or melting of material that has already been deposited and to ensure the dimensional stability of the three-dimensional object 410 .

zum Zeitpunkt des Austrags, $$\underset{\mathrm{t}}{\max }\left[\mathrm{T}\left({\mathrm{r}}_{\mathrm{i}},\mathrm{t}\right)\right]\le {\mathrm{T}}_{\max }.$$

für alle Zeiten.The temperature curve at location r _i must therefore fulfill the following condition: $$\mathrm{T}\left({\mathrm{right}}_{\mathrm{i}},{\mathrm{t}}_{\mathrm{i}}\right)\ge {\mathrm{T}}_{\mathrm{at\; least}},$$

at the time of discharge, $$\underset{\mathrm{t}}{\mathrm{Max}}\left[\mathrm{T}\left({\mathrm{right}}_{\mathrm{i}},\mathrm{t}\right)\right]\le {\mathrm{T}}_{\mathrm{Max}}.$$

for all time.

In this case, t _i is the point in time at which material is discharged at location r _i . For each layer, the temperatures T(r _i ,t) can be determined by integrating equation (1.3). The initial temperature distribution of the surface at the beginning of the layer construction and the geometry-dependent heat loss coefficients, such as the model of the three-dimensional object in equations (1.4) - (1.6) or the model in (1.7), are used as parameters. The relative trajectory of the discharge nozzle 210 (and any additional heat sources present) with respect to the object surface can be determined from the instructions of the machine code. The additional heat source can be arranged on the discharge nozzle 210 and can be moved relative to it. This defines both the geometry of the three-dimensional object 410 in the layer under consideration and the time-dependent distance to the heat sources. The latter results - together with the spatial distribution of the radiation amplitude - in the time-dependent power of the heat sources radiated onto the object's surface.

The method is preferably carried out with foresight, ie at least before the material is discharged for at least one volume element 110 or also for parts of the or the complete three-dimensional object 410. This is done by predictively calculating the temperature of the volume element 110 for each discrete position and affecting the at least one heat source 640 and the at least one heat sink by adapting the machine code and the boundary conditions for temperature increase and temperature decrease. As a result, before the volume elements 110 arise, their influence on the production of the object 410 can advantageously be taken into account and influenced in order to optimize the object.

• Veränderung der Prozessgeschwindigkeiten, z.B. die des Trägers 620 des herzustellenden Gegenstands und/oder der mindestens einen Austragseinheit 630 (Fig. 6),
• Steuerung der abgestrahlten Leistung der mindestens einen Wärmequelle 640 (Fig. 7),
• Steuern mindestens einer Wärmesenke 650 (Fig. 7),
• Einfügen von zusätzlichen Verfahrbefehlen oder auch Wartebefehlen,
• Veränderung der Reihenfolge der ausgetragenen Elemente (Konturen, Fülllinien),
• Veränderung der Beschaffenheit von Füll- und /oder Komturlinien, wie z.B. Aufspaltung in mehrere einzelne Fülllinien mit jeweils angepasster Geschwindigkeit und/oder Umwandlung in Einzelaustrag.

If the calculated, location- and time-dependent surface temperature T(r,t) violates one of the two conditions (1.9 or 1.10), at least one or a combination of the following measures can be taken:

• Changing the process speeds, e.g. that of the carrier 620 of the object to be produced and/or the at least one discharge unit 630 ( 6 ),
• Control of the radiated power of the at least one heat source 640 ( 7 ),
• Controlling at least one heat sink 650 ( 7 ),
• Insertion of additional movement commands or waiting commands,
• changing the order of the drawn elements (contours, filling lines),
• Changing the nature of filling and/or compass lines, such as splitting into several individual filling lines, each with an adjusted speed and/or conversion to a single discharge.

This is done with the aim of influencing the energy brought in by the heat source(s) and given off by heat losses on the object's surface in such a way that both of the above conditions (1.9 and 1.10) are met after the measures have been carried out.

This procedure, which is shown in the flowchart of the 3 shown changes the machine code and thus the results of the temperature calculation T(r,t). It is therefore advantageous to determine the temperatures T(r,t) again on the basis of the adapted machine code in order to increase the accuracy of the method. The steps described above are repeated until conditions (1.9) and (1.10) are met.

Block 310 describes the input data in the form of a 3D volume, for example an STL or the layer stacks that describe the 3D volume (for example CLI). An STL is a CAD data format that describes the outer geometry of the three-dimensional object (visible contour of the 3D volume) and a CLI is a CAD data format that describes a layer stack of contour lines of the 3D volume. In block 320, according to the internal and external shape of the object 410 to be manufactured, a the corresponding machine code is created, which, in addition to the individual geometric positions in three-dimensional space, also contains the other boundary conditions for the drawing of the respective volume element 110. These boundary conditions correspond to the measures specified above. When the differential equation (1.3) given above is then solved in block 340, the initial temperature field (installation space temperature or temperature of the object) is also included in block 330 when each volume element 110 is discharged. For each volume element 110 to be removed, block 350 checks whether the above conditions (1.9, 1.10) are met. In the positive case, the machine code can then be output in block 370. In the negative case, the machine code must be modified, and it can also be expanded. The rest of the sequence is then again identical to the blocks following block 320.

The calculations of the method are preferably carried out offline, i. H. before actually creating the 3D object. However, they can also be carried out online. A criterion for this can B. the available computing power. A numerical model approach is preferably used for the necessary calculations, but an empirical or analytical approach can also be used.

Figures 4 and 5 illustrate the distinction between fill lines 510 and contours 530 of the three-dimensional object, wherein in figure 5 the interconnected volume elements 130 of the outer contours 530 and inner filling lines 510 are shown and a possible discharge order and discharge direction 520 of the volume elements 110, 120 are illustrated schematically using the dashed arrow.

With the support of the claimed method for thermal process management, at least one three-dimensional object 410 is produced by means of additive manufacturing by discharging volume elements 110 of a specific size per unit of time, preferably by sequential discharging, of at least one fluid solidifiable material at a specific temperature using at least one discharge nozzle 210 Discharge unit 630 according to a device controllable by the method Figures 6, 7 for generating the three-dimensional object 410 at discrete positions in a construction space 610 according to a predetermined model of the three-dimensional object 410. In particular, drops and strands come into consideration as volume elements, since in both cases volume elements of a certain size are discharged per unit of time.

The model is part of a computer-implemented machine code that defines the discrete positions of the volume elements 110 to be extracted and boundary conditions for their extraction. For each discrete position in three-dimensional space, the temperature of the volume element 110 is calculated and the thermal energies generated by at least one heat source 640 and at least one heat sink 650 according to FIG 7 introduced into or removed from the construction space 610 and discharged through heat losses in the construction space 610. Such heat losses can, for example, also be heat losses to neighboring volume elements. Likewise, adjacent volume elements and, for example, the discharge nozzle can be possible sources of heat. There can be one or more discharge units 630 each with one or more discharge nozzles.

• Feststellen, ob die berechnete Temperatur des aktuellen Volumenelements 110 zum aktuellen Zeitpunkt an der aktuellen diskreten Position innerhalb eines materialspezifischen Intervalls liegt,
• Feststellen, ob die berechneten Temperaturen der benachbarten Volumenelemente 120, 150 in einem betrachteten Zeitintervall von einem vorigen bis zum aktuellen Zeitpunkt unterhalb einer materialspezifischen Temperaturobergrenze liegen,
• falls die berechnete Temperatur am Ort des aktuellen Volumenelements 110 innerhalb des materialspezifischen Intervalls und die Temperaturen der benachbarten Volumenelemente 120, 150 im betrachten Zeitintervall unterhalb der materialspezifischen Temperaturobergrenze liegen:
• Fortfahren mit dem Feststellen der Temperatur des nächsten Volumenelements 110 an der nächsten diskreten Position zu einem nächsten zugeordneten diskreten Zeitpunkt,
• Fortfahren mit dem Feststellen der Temperaturen der benachbarten Volumenelemente 120, 150 bis zum nächsten zugeordneten diskreten Zeitpunkt,
• falls die berechnete Temperatur außerhalb des materialspezifischen Intervalls liegt oder die Temperaturen der benachbarten Volumenelemente 120, 150 im betrachten Zeitintervall oberhalb der Temperaturobergrenze liegen:
• Anpassen des Maschinencodes und/oder der Randbedingungen zur Temperaturerhöhung und Temperaturverminderung mindestens an der aktuellen diskreten Position,
• Fortfahren mit dem erneuten Feststellen der Temperatur des aktuellen Volumenelements 110 an der aktuellen diskreten Position,
• Fortfahren mit dem erneuten Feststellen der Temperaturen der Volumenelemente 120, 150,

wobei die Schritte für mindestens einen Teil des Modells des dreidimensionalen Gegenstands 410 ausgeführt werden.The procedure includes the following steps:

• Determining whether the calculated temperature of the current volume element 110 at the current time at the current discrete position is within a material-specific interval,
• Determining whether the calculated temperatures of the neighboring volume elements 120, 150 in a considered time interval from a previous to the current time are below a material-specific upper temperature limit,
• if the calculated temperature at the location of the current volume element 110 is within the material-specific interval and the temperatures of the neighboring volume elements 120, 150 are below the material-specific upper temperature limit in the time interval under consideration:
• proceeding to determine the temperature of the next volume element 110 at the next discrete position at a next associated discrete time,
• continuing to determine the temperatures of the neighboring volume elements 120, 150 until the next assigned discrete point in time,
• if the calculated temperature is outside the material-specific interval or the temperatures of the neighboring volume elements 120, 150 are above the upper temperature limit in the considered time interval:
• Adapting the machine code and/or the boundary conditions for temperature increase and temperature decrease at least at the current discrete position,
• proceeding to re-determine the temperature of the current volume element 110 at the current discrete position,
• Proceeding to re-determine the temperatures of the volume elements 120, 150,

wherein the steps are performed for at least a portion of the model of the three-dimensional object 410.

The above steps of the method can, for. B. only for the currently to be discharged volume element 110 and an adjacent volume element 120 or for several preferably discrete neighboring volume elements 110, 120 are executed in the X, Y or Z direction, so that it is executed for only one row, several rows, one layer, several layers or the complete object 410, for example. If necessary, this can also be done in advance for one or more volume elements 110, 120 or also for a part or the complete model of the three-dimensional object.

Advantageously, previously defined, material-dependent upper temperature limits are not exceeded at any time in order to avoid melting or softening and/or deliquescence of material that has already been deposited and to ensure the dimensional stability of the three-dimensional object

The material-specific interval can be defined, for example, in that a complete merging of the current volume element 110 with neighboring volume elements 120, 150 can take place within this interval. The material-specific upper temperature limit can be defined, for example, by the fact that the dimensional stability of the volume elements is guaranteed below this upper temperature limit.

In a first embodiment of the method, which increases the accuracy of the local temperature calculation, for each discrete position in three-dimensional space to calculate the temperature of volume element 110, the thermal energy that enters installation space 610 from the at least one discharge nozzle 210 of the at least one discharge unit 630 and /or at least one heat source and heat sink arranged on the at least one discharge nozzle 210 in installation space 610 and which act on volume element 110, and the thermal energy that enters installation space 610 from volume element 110 to at least directly adjacent volume elements 120 and emitted to the environment as thermal radiation and free convection must be taken into account.

In a further embodiment of the method, which increases the accuracy of the local temperature calculation while reducing the computational effort, the thermal energies that are relevant for the calculation of the temperature of volume elements 110 for each discrete position in three-dimensional space and that are generated by at least one heat source and at least a heat sink in and out of the construction space 610 and discharged through heat losses in the construction space 610, enter into a differential equation within the model of the three-dimensional object and the machine code, wherein parts of the differential equation can be linearized to solve them.

In an additional embodiment of the method, which further optimizes the temperature distribution in the three-dimensional object 410, the temperature of the volume element 120 can also be recalculated for at least one of the directly adjacent discrete positions and, based on this, the machine code and/or the possibly associated boundary conditions for the temperature increase and temperature reduction for at least this discrete position.

In addition, with advantageous optimization of the temperature distribution in the three-dimensional object 410, the temperatures of the volume elements 120 can also be recalculated for all other discrete positions and, based on this, the machine code and/or the possibly associated boundary conditions for the temperature increase and temperature reduction can be adapted for these discrete positions.

In another embodiment of the method, which increases the accuracy of the local temperature calculation, a relative trajectory of the at least one discharge nozzle 210 and, if applicable, at least one additional heat source arranged on the at least one discharge nozzle and at least one heat sink with respect to the surface of a den carrier 620 carrying the three-dimensional object 410 to be produced and/or the object 410 are determined. In particular, the carrier 620 can also be temperature-controlled.

• das Verändern der Prozessgeschwindigkeit des Austrags, wobei dieses z.B. über das Verändern der Fahrgeschwindigkeiten des Trägers 620 herzustellenden Gegenstands 410 und/oder der mindestens einen Austragseinheit 630 erreichbar ist;
• das Steuern der abgestrahlten Leistung der mindestens einen Wärmequelle;
• Steuern mindestens einer Wärmesenke
• das Einfügen von zusätzlichen Verfahrbefehlen oder auch Wartebefehlen;
• das Verändern der Reihenfolge der diskreten Positionen, an denen nacheinander Volumenelemente 110, 120 ausgetragen werden. Dabei können z. B. zunächst einzelne Konturen ausgetragen werden, unterbrochen vom Austrag von Fülllinien;
• das Verändern der Beschaffenheit von Fülllinien, wie z.B. Aufspaltung in mehrere einzelne Fülllinien mit jeweils angepasster Geschwindigkeit und/oder Umwandlung in Einzelaustrag, wobei Konturen oder Fülllinien beispielsweise in der Art ausgetragen werden, dass nur prozesstechnische Pausen zwischen den einzelnen Austrägen erfolgen, diese also kontinuierlich ausgetragen werden, oder zusätzliche, prozesstechnisch nicht notwendige Pausen eingefügt werden, wodurch die Temperatur gesenkt wird.

Another embodiment of the method that provides alternatives for adjusting the local temperatures can include adjusting the boundary conditions using at least one or a combination of the following measures:

• changing the process speed of the discharge, whereby this object 410 to be produced and/or the at least one discharge unit 630 can be reached, for example, by changing the travel speed of the carrier 620;
• controlling the radiated power of the at least one heat source;
• Controlling at least one heat sink
• the insertion of additional movement commands or waiting commands;
• changing the order of the discrete positions at which volume elements 110, 120 are successively discharged. In doing so, e.g. B. first individual contours are discharged, interrupted by the discharge of filling lines;
• changing the nature of filling lines, such as splitting them into several individual filling lines, each with an adjusted speed and/or converting it to a single discharge, with contours or filling lines being discharged in such a way that only process-technical pauses occur between the individual discharges, i.e. these be discharged continuously, or additional breaks that are not necessary for the process are inserted, which lowers the temperature.

Preferably, depending on the absorption spectrum of the material used, one or more thermal radiation sources, such as e.g. B. infrared emitters and / or one or more non-thermal radiation sources such. As laser, LED and / or gas discharge lamps can be used. Since these can be arranged movably and independently of one another on the respective discharge nozzle, specific volume elements can be additionally heated in a targeted manner, e.g. the current volume element 110 and/or also neighboring volume elements 120. The choice of the radiation source can depend on the absorption spectrum of the plastic used judge.

In a next advantageous embodiment of the method, an additional forced convection can be caused to reduce the temperature of the volume element 110 at the discrete position. B. at least one fan and / or at least one controllable heat sink can be used optionally.

Preferably, at least two materials with different specifics can be used as fluid solidifiable materials for the purposeful adjustment of the properties of the three-dimensional object.

For this purpose, in order to specifically adapt the properties of the three-dimensional object 410 and to maintain its dimensional stability when using at least two materials with different specifics that cannot tolerate the same, necessary installation space temperature, the temperature of the volume element can be increased when the installation space temperature is set to the lower of the two temperatures 110, which requires the higher fusion temperature, is increased or reduced for its application, and/or when the installation space temperature is set to the higher of the two temperatures, the temperature of the volume element 110, which requires the lower fusion temperature, is reduced or increased for its application. These steps can also be combined, i.e. a higher temperature with heating and/or a lower temperature with cooling can also be applied to neighboring volume elements. If necessary, the temperature at the discharge point can also be subsequently increased or reduced after the discharge.

Especially in multi-material systems, through targeted influencing of the boundary conditions and the temperature(s), be it for example in the installation space, on the carrier or in the material itself, advantageous framework conditions can be created that also allow materials with different specifics to be reliably combined with one another to connect or unite.

Preferably, when using more difficult to process materials, especially when using high-temperature materials such. B. PEI, PSU, PPSU, PEEK, PEAK, PEK or PPS, the necessary space temperature can not be realized, the temperature of the volume element 110 can be increased to its order.

In another embodiment of the method, which additionally favors the diffusion of the volume elements 110, 120 and/or z. B. in the case of partially crystalline plastics, the morphology development is influenced or specifically controlled, the volume elements 120 or 150 discharged to form a filling line and/or contour line can be heated/cooled after the filling line and/or contour line has been completely discharged. In this way, for example, stresses in the three-dimensional object can also be avoided, since large temperature differences in the object can be avoided.

In principle, it is also possible to heat or cool the surface of a carrier 620 carrying the three-dimensional object 410 to be produced or of the three-dimensional object 410 to be provided with volume elements not only during material discharge, but also without material discharge. Such a temperature-controlled building carrier 620 can act like an extension of the installation space heating (same temperature settings), e.g. to ensure homogeneous temperature control of the three-dimensional object 410 by e.g. creating the same temperature conditions on all component sides. This helps to avoid tension and thus minimize distortion.

In a further advantageous embodiment of the method, by which the mechanical properties of the three-dimensional object 410 can be predicted, a morphology development of the object 410 based on a temperature development can be determined by means of a simulation.

The development of morphology can be favored by deliberately maintaining or increasing or decreasing the ambient temperature. In particular, the temperatures in the construction space 610 and those of the preferably temperature-controlled carrier 620 have an influence on the ambient temperature.

The method according to one of its embodiments can be used to produce a three-dimensional object 410 by means of additive manufacturing by discharging volume elements 110, 120 of a certain size per unit of time at least one fluid solidifiable material with a certain temperature at discrete positions in three-dimensional space in a device controllable by the method with at least one discharge nozzle 210 at least one discharge unit 630 can be used, whereby volume elements 110 are discharged in a construction space corresponding to a model of the three-dimensional object 410.

The method according to one of its embodiments can also be used in a device with at least one discharge nozzle 210 at least one discharge unit 630 for producing a three-dimensional object 410 by means of additive manufacturing by discharging volume elements 110, 120 of a specific size per unit of time, preferably by sequential discharging, of at least one fluid solidifiable Material are performed with a certain temperature at discrete positions in three-dimensional space, which discharges volume elements 110 in a construction space corresponding to the model of the three-dimensional object 410 . The device has at least one heat source and at least one heat sink, which in turn can preferably be arranged in the area of the discharge nozzle.

A further exemplary embodiment is a computer program product with a program code, which is stored on a computer-readable medium, for carrying out at least one of the methods described above while achieving the advantages mentioned.

Reference List

110

currently swept volume element

120

previously swept volume element

130

first molecular chain

140

second molecular chain

150

connected solid

160

intertwined chains of molecules

210

discharge nozzle

220

T _air

230

T _environment

240

T _component

250

it

260

Q̇ _K

270

Q̇ _HS

280

Q̇ _W

290

german/german

310

STL/CLI

320

create machine code

330

Initial temperature field at the beginning of the shift

340

Solving the differential equation

350

Checking the boundary conditions

360

Modify and extend machine code

370

Output machine code

410

three-dimensional object

510

filling

520

filling line railway

530

contour

610

installation space

620

Carrier of the 3D object to be manufactured

630

discharge unit

640

heat source

650

heat sink

Claims (16)

Method for thermal process control, by means of which at least one three-dimensional object (410) is produced by means of additive manufacturing by discharging volume elements (110, 120) of a certain size per unit of time of at least one fluid solidifiable material with a certain temperature by means of at least one discharge nozzle (210) of at least one discharge unit (630) of a device that can be controlled by the method for generating the at least one three-dimensional object (410) at discrete positions in a construction space (610) according to a predetermined model of the three-dimensional object (410), wherein the model of the three-dimensional object (410 ) is part of a computer-implemented machine code that defines the discrete positions of the volume elements (110) to be discharged and boundary conditions for their discharge, and wherein the temperature of the volume element (110) is calculated for each discrete position in three-dimensional space and the thermal energies generated by at least a heat source (640) and at least one heat sink (650) are introduced into the construction space (610) or removed from the construction space and are released through heat losses in the construction space (610), are taken into account,
characterized,
that the procedure includes the following steps: - determining whether the calculated temperature of the current volume element (110) at the current time at the current discrete position is within a material-specific interval, - Determining whether the calculated temperatures of the neighboring volume elements (120, 150) in a considered time interval from a previous to the current time are below a material-specific upper temperature limit, - if the calculated temperature at the location of the current volume element (110) is within the material-specific interval and the temperatures of the neighboring volume elements (120, 150) are below the material-specific upper temperature limit in the considered time interval: • proceeding to determine the temperature of the next volume element (110) at the next discrete position at a next assigned discrete time, • Continuing to determine the temperatures of the neighboring volume elements (120, 150) until the next assigned discrete point in time, - if the calculated temperature is outside the material-specific interval or the temperatures of the neighboring volume elements (120, 150) are above the upper temperature limit in the considered time interval: • Adaptation of the machine code and the boundary conditions for temperature increase and temperature decrease at least at the current discrete position, • proceeding to re-detect the temperature of the current volume element (110) at the current discrete position, • Proceed with re-determining the temperatures of the volume elements (120, 150), wherein the steps are performed for at least a portion of the model of the three-dimensional object (410). Method according to Claim 1, characterized in that for each discrete position in three-dimensional space for calculating the temperature of the volume element (110), the heat energies that enter the installation space from the at least one discharge nozzle (210) of the at least one discharge unit (630) and/or at least one heat source (640) and heat sink (650) arranged on the at least one discharge nozzle (210) in the installation space (610) and which act on the volume element (110), and the thermal energy entering the installation space (610 ) are emitted from the volume element (110) to at least directly adjacent volume elements (120) and to the environment as thermal radiation and free convection. Method according to one of Claims 1 or 2, characterized in that the thermal energies which are relevant for the calculation of the temperature of volume elements for each discrete position in three-dimensional space and which are generated by at least one heat source (640) and at least one heat sink (650) in are entered and removed from the installation space (610) and are released through heat losses in the installation space (510), enter into a differential equation within the machine code, with parts of the differential equation being able to be linearized to solve it. Method according to one of the preceding claims , characterized in that the temperature of the volume element (120) is additionally recalculated for at least one directly adjacent discrete position and/or for at least one other discrete position and that based thereon the machine code and/or the boundary conditions for Temperature increase and temperature decrease can be adjusted for at least this discrete position. Method according to one of the preceding claims, characterized in that if the calculated temperature of any point on the already discharged surface is above a defined temperature limit at a point in time, a certain number of calculation steps before this point in time is reversed and adjustments to the machine code and/or of the boundary conditions for the temperature increase and temperature decrease are carried out at least in the newly calculated time interval. Method according to one of the preceding claims, characterized in that a relative trajectory of the at least one discharge nozzle (210) and, if applicable, at least one additional heat source (640) and heat sink (650) arranged on the at least one discharge nozzle (210) is determined from machine code commands with respect to the surface of a preferably temperature-controlled carrier (620) carrying the three-dimensional object (410) to be produced and/or of the three-dimensional object (410). Method according to one of the preceding claims, characterized by predictive calculation of the temperature of the volume element (110) for each discrete position of the at least part of the model and influencing the at least one heat source (640) and the at least one heat sink (650) by adapting the machine code and the boundary conditions for temperature increase and temperature decrease. Method according to one of the preceding claims, characterized in that the adaptation of the boundary conditions comprises at least one or a combination of the following measures: - changing the process speed, - Controlling the radiated power of the at least one heat source (640), - controlling the at least one heat sink (650), - tempering of the carrier (620), - Insertion of additional movement commands or waiting commands, - changing the order of the discrete positions at which volume elements (110, 120) are successively discharged, - Changing the nature of fill lines and/or outlines. Method according to one of the preceding claims, characterized in that an additional forced convection is caused to reduce the temperature of the volume element (110) and / or adjacent volume elements at the discrete position, to generate z. B. at least one fan and / or at least one controllable heat sink (640) is used. Method according to one of the preceding claims, characterized in that at least two materials with different specifics are used as fluid solidifiable materials, wherein when using the at least two materials, if they do not tolerate the same necessary installation space temperature, when the installation space temperature is set to the lower of the two temperatures, the temperature of the volume element (110) that requires the higher fusion temperature, to whose order is increased or decreased, and/or when the installation space temperature is set to the higher of the two temperatures, the temperature of the volume element (110), which requires the lower fusion temperature, is reduced or increased for its application. The method according to claim 9 or 10, characterized in that when using high-temperature materials, such as. B. PEI, PSU, PPSU, PEEK, PEAK, PEK or PPS, the necessary space temperature can not be realized, the temperature of the volume element (110) is increased to the order. Method according to one of the preceding claims, characterized in that the surface of a carrier (620) carrying the three-dimensional object (410) to be produced or of the three-dimensional object (410) to be provided with volume elements (110) is not only heated or cooled during material discharge, but even without material discharge. Method according to one of the preceding claims, characterized in that the volume elements (110) discharged to form a filling line and/or contour line are heated or cooled after the filling line and/or contour line has been completely discharged. Method according to one of the preceding claims, characterized in that a morphology development of the three-dimensional object (410) based on a temperature development is determined by means of a simulation of the method. Device with at least one discharge nozzle (210), at least one discharge unit (630) and at least one heat source (640) and at least one heat sink (650) in a construction space (610) for carrying out the method according to one of Claims 1 to 14, which is set up for this purpose , for producing at least one three-dimensional object (410) by means of additive manufacturing by discharging volume elements (110, 120) of a certain size per unit of time at least one fluid solidifiable material with a certain temperature at discrete positions in three-dimensional space, and is configured to, in a construction space (610) corresponding to a model of the three-dimensional object (410) to discharge volume elements (110). Computer program product with a program code, which is stored on a computer-readable medium, for carrying out the method according to one of Claims 1 to 14 by means of the device according to one of Claims 15.

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